This invention relates generally to micro-image techniques for recording and reproducing data, and more particularly to a microfiche bearing a set of images each representing a page of data which is viewable on the screen of a microfiche reader and a companion set of reversed images each of which, when displayed on the screen, may be directly copied.
In order to conserve storage space and afford a convenient means for retrieving information, it is now common practice to photograph documents, records, the pages of books and various forms of technical data in a sharply reduced scale on microfilm. Conventionally, a micro-scale image of each page or document is recorded on a separate frame on a microfilm roll. To view the recorded data, the roll is inserted in a reader or optical projector and the film is advanced therein to place a selected frame into an optical gate whereby an enlarged and readable image is cast on a screen.
More recently, a new storage technique has been developed wherein a group of microfilm images are placed on a single record sheet rather than along a film roll. In such microrecords, which are known commercially as "microfiches," the micro-scale images are generally arranged serially along parallel rows, whereby the micro-images are distributed in a grid formation on the sheet. A microfiche is useful where one wishes to incorporate on a single reproducible sheet, interrelated documents or other information pertaining to a particular subject matter. Thus, with a single microfiche, one may record all of the pages of a printed patent.
In order to make use of the microfiche, the user requires an optical reader. This reader must include a mechanism to shift the microfiche in the X and Y directions, in order to align a particular frame with the optical system serving to project an enlarged image of the selected frame onto the screen.
In a conventional microfiche reader, when a selected image frame is projected onto the screen, the image displayed thereon is erect and therefore suitable for direct viewing. But one cannot make a photographic copy of the displayed image by placing a sensitive film against the screen, for then the image developed on the sensitive surface of the film will be a reversed or mirror image of the screen image.
In order, therefore, to provide a non-reversed and readable copy, it is presently necessary to interpose a plane mirror in the path between the projection system of the reader and the sensitive film in the copier. Since the image formed by the plane mirror is erect, reversed (right side appears as left side) and the same size as the object, the reversed image projected by the mirror on the sensitive surface of the film gives rise to a developed image thereon that is properly oriented.
The practical objection to the conventional copier arrangement for microfiche readers and other apparatus adapted to make copies of microfiche images, is that the requirement for a mirror stands in the way of producing a highly compact reader-copier machine. Because the mirror must be interposed between the projection system of the reader and the film or other sensitive media in the copier (such as a xerographic plate) the structure must be sufficiently commodious to accommodate this spatial requirement.
In my U.S. Pat. No. 3,704,068 there is disclosed a micro-image technique in which the pages of data are not recorded in discrete frames on a microfiche but are dissected and interlaced thereon to produce a multiple image record which may be read-back by selectively enlarging only the pattern of dispersed characters or bits which together constitute the data of a single page. A significant advantage of this technique is that it makes possible a highly compact reader whose dimensions are comparable to those of a standard book. But even with a reader of this type, one cannot make copies of the illuminated image formed onto the screen unless a mirror is interposed between the sensitive film and the screen, as a consequence of which the arrangement is no longer exceptionally compact.